Submarine signaling



Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE SUBMARINE SIGNALING Bertram M. Harrison, Wellesley Hills, Mass., as-

signor, by mesne assignments, to Submarine Signal Company, Boston, Mass, a corporation of Delaware 2 Claims.

The present application is a division of application Serial No. 339,922, filed June 11, 1940.

The present invention relates to echo rangin systems employing underwater compressional wave transmitters and more particularly to frequency control arrangements for such systems.

In echo ranging systems it has heretofore been proposed to transmit a compressional wave impulse by means of an underwater transmitter electrically energized at the desired frequency by current supplied from a vacuum tube oscillator in which the frequency was controlled by a tuned tank circuit containing a variable condenser. Such arrangements required positioning the tuning condenser in the vicinity of the vacuum tube oscillator. It is often desirable, however, to place the system controls at a point remote from the oscillator or to have a plurality of controls at various points. It is an object of the present invention to provide an arrangement for controlling the frequency of the oscillator from a remote point or from a plurality of remote points.

In my copending applications Serial No. 1'74,- 081, filed November 11, 1937, No. 231,390, filed September 23, 1938, and No. 231,391, filed September 23, 1938, I described echo ranging systems in which the frequency of the transmitted compressional wave was varied during the period of transmission. It is a further object of the present invention to provide a simple and efficient arrangement for automatically varying the frequency of the transmitted signal through a predetermined but adjustable frequency range in any desired direction of frequency change.

In my copending application Serial No. 314,- 803, filed January 20, 1940, I described an echo ranging system employing a compressional wave signal continuously fluctuating in frequency back and forth between predetermined limits. It is a further object of the present invention to provide a simple and efficient arrangement for automatically obtaining such a frequency fluctuation in the transmitted compressional wave signal, and one which can be controlled from a plurality of points.

A still further object of the present invention is to provide an alternating current source for operating an underwater transmitter through a very wide range of frequencies.

The above and other objects of the present invention as well as the construction and operation of the same will best be understood from the following description taken in connection with the accompanying drawing in which Fig. 1 represents a schematic wiring diagram of a control system in accordance with the present invention and Fig. 2 shows schematically a modification of the invention.

As shown in Fig. 1, a compressional wave transmitter l is supplied with electrical energy of the desired frequency, preferably in the supersonic range, through an amplifier 2 energized by a vacuum tube oscillator. The oscillator tube 3 may be of any suitable form; it is here shown as a triode having a cathode 4, grid 5 and anode 6. The anode-cathode circuit of the oscillator includes a tank circuit 1 comprising an inductance 8 shunted by a condenser 9, these elements having such magnitudes that the circuit 1 is resonant at some average frequency. The grid 5 is connected to the cathode 4 through a resistor Ill. The grid circuit is coupled to the anode circuit through condenser H and inductance [2 in such a manner that sustained oscillations can be obtained. Anode potential for the oscillator is supplied from the terminals marked B+ and B-, the ground connection being completed through the key 22.

In parallel with the tank circuit 1 there is a second vacuum tube circuit which may be designated as a reactor tube circuit. This includes the triode tube I3 having cathode l4, grid 15 and anode [6. The anode circuit of the tube includes a resistor H in series with a capacitor l8, these elements being also in parallel with the tank circuit 1. The grid I5 is connected to the junction of the resistor l1 and condenser l8 through a large blocking condenser IS. The cathode M is connected to the common or ground lead 20.

It will now be observed that the alternating current flowing through resistor l1 and condenser l8 will be substantially in phase with the voltage across the tank circuit 1 which is in parallel with the series connected resistance l1 and condenser l8 since the condenser I8 is ven a relatively small value of capacitive reactance compared with the magnitude of resistance H. The voltage across the condenser I8, however, is in quadrature with the voltage across the tank circuit. This results in the application to the grid l5 of an alternating voltage which is in quadrature with the voltage across the tank circuit. Similarly, the plate current in the tube l3 will be in quadrature with the current through the tank circuit. The reactor tube circuit, therefore, acts as an inductance in parallel with the oscillator tank circuit and thereby changes the resonant frequency of the latter. The magnitude of this inductance depends upon the plate current flowing through the tube l3. Control of this current and therefore control of the frequency of the oscillator 3 can be obtained byapplying to the grid I5 a controllable potential. Making the grid more positive causes an increase in the plate current and therefore a decrease in the inductance in parallel with the tank circuit, resulting in an increase in the oscillators frequency. A direct potential may, for example, be applied to the terminals 23 and 24 of the double-pole, double-throw relay 25, the grid I 5 being connected to the terminal 24 through the current-limiting resistor 28 and the cathode being connected to the terminal 23. This potential may be supplied in any desired manner, for example, through an adjustable potentiometer energized from a suitable source of direct current.

For maximum frequency change the direct potential is adjusted so that the tube l3 can be "operated at any point between saturation and cut-off. Moreover, the internal impedance of the reactor tube with maximum positive grid voltage should be kept at a minimum in order to provide alarge possible range of frequencies for the oscillator output. I prefer to employ a tube whose characteristics are such that its internal impedance with maximum positive grid potential is-approximately equal to the reactance of the oscillator tank circuit inductor at the highest desired signaling frequency.

The control potentiometer can, of course, be placed at any desired point remote from the reactor tube and oscillator. A suitable arrangement "of this type is shown in the upper portion of Fig. 1. Since, however, it is usually desirable to provide for such a control at more than one station, I have illustrated two contro1 stations. One of these may be eliminated or others added as will readily be understood by those skilled in the art. Assuming the relay 25 to be in its upper position, as shownQthe grid-cathode circuit of tube 13 will be connected to the conductors 21 and 28. The two control stations are indicated at 29 and 30. At each station there is a source of direct potential'across which there are connected potentiometers 3| and 32; Each station is also provided with a double-pole, double-throw switch 33 and 34. The switch 33 is provided with a pair of movable contacts 35 and 36 and two pairs of stationary contacts 31 to 43. The switch 34 is provided with movablecontacts H and 42 and stationary contacts 43 to 46. The stationary contacts oft-hetwo switches are connected together as shown, contact 3'! beingconnected to 43, contact 38 to 46, contact 39 to 46 and contact 450 to 45. The movable contacts of switch 33 are connected together and to conductor 28-. The movable contact-4| of switch 34 is connected by the lead 4'! to the movable contact 48 of potentiometer 3! and contact 52 is connected to the movable contact 49 of potentiometer 32. Finally, the conductor 21 is connected to the negative terminals of both of the potentiometers 3| and 32.

With this arrangement it is possible for an operator at either station to control the frequency of the oscillator 3 and therefore of the compressional waves produced by the transmitter 1 by varying the position of the potentiometer at his station. Assuming that the switches 33 and-34 at the two stations are both thrown to'the left position, as shown, the operator at station 29 has control and the operator at station 30 has not. This can be seen by following contween the grid and cathode of the tube It, thereby varying the magnitude of the anode current through the tube 13 and consequently varying the frequency of the oscillator 3. Adjustment of the potentiometer 39 at station 39, however, has no effect since the ci cuit of this potentiometer is open at terminal 4Q at station 29.

Should, however, the operator at station 30 desire to take control, it is only necessary for him to throw switch 34 to the right. The grid circuit of tube 5.3 will then be completed from conductor 28 through contacts 35 and 39 of switch 33, contacts 36 and '42 of switch 34, potentiometer, contact 49 to the negative terminal of the direct current supply and thence by conductor 53 to conductor 2?. In this manner contro1 of the frequency can be taken at either of the two stations.

A further feature of this arrangement is that the frequency of the oscillator 3 can be indicated at each station at all times by the simple provision of a voltmeter at each station.' At station 29 voltmeter 5| is connectedacross the conductors 27 and 28. A similarly connected meter 52 is provided at station 3-3. Both of these meters, therefore, indicate the direct grid potential applied across the grid circuit of the tube Hi. The meters can, therefore, be calibrated directly interms of the frequency of the oscillator 3 Thus, not only does my invention make possible the provision of a frequency contro1 of the oscillatorfrom one or more remote points without the necessity of piping high frequency currents through long cables, but also it provides for an indicator of the frequency at each of the remote points.

As abovementioned, I. proposed in my copending application Serial No. 314,803 that in an echo ranging system a compressional wave signal be employed which continuously fluctuates in frequency back and forth between predetermined limits. The present invention is also applicable to produce such a signal of fluctuating frequency. For this purpose I provide transformer having its secondary windin El connected in series in the lead 28. The primary winding 68 of the transformer is connected to the output of an oscillator 22, which may be of conventional design, whose frequency is equal to the desired rate of frequency fluctuation which will usually be within the audiofrequency range. This oscillator is arranged so that it can be started by short-circuiting the terminals H and stopped by open-circuiting these terminals. The oscillator 12 maybe turnedon and off at either of the two stations 29 or 30 by providing at each station a single-pole, double-throw switch, for example, 69 and F8, respectively. The movable elements of the switches 89 and it are each. respectively connected to one of the on-off terminals H of the oscillator l2 while the stationary contacts of the switch 69 are connected to thecorresponding contacts of switch Hi. Inthe switch positions shown in l the audio oscillator is turned off. To start it either switch "may be "thrown to the left position. This arrangement introduces an audio frequency.potential'into the grid circuit of tube I 3, this potential being superimposed upon the potential provided by the potentiometers 3| or 32. Adjustment of these potentiometers in this case controls the mean value of the frequency of the oscillator 3 above and below which the frequency fluctuations take place at a rate corresponding to the frequency of the oscillator 12. This mean frequency will be indicated by the meters 5| and 52.

It will be understood that a compressional wave signal is emitted by the transmitter i only when the key 22 is depressed. This key may be operated automatically as by the time interval measuring apparatus in echo ranging systems, or it may be operated by hand. In either case the key may be placed at any desired point or separate keys may be supplied at the various control stations. For the arrangements so far described, the lower part of key 22 is not used.

The reactor-tube-oscillator circuit may also be employed to produce a signal whose frequency varies automatically between specified limits. For this purpose the relay 25 is caused to take its lower position so that the terminals 23 and 24 are connected to the conductors 52 and 53, respectively. These conductors are connected across grid return resistor 55 and a condenser 55 which is normally short-circuited through the upper contact 51 of the lower element 58 of key 22 and conductors 59 and 60. Conductor 52 includes in series a battery 54 which, through resistor 55, places a negative bias on the grid l5 which is adjusted to give some average value of reactor tube plate current. Between the lowercontact 6| of the key element 58 and conductor 60 there is connected an adjustable series resistance 62 in series with an adjustable portion of a potentiometer 63 supplied from a suitable direct current source through a double-pole, double-throw switch 64. It will be evident that when the switch 64 is closed, the condenser 56 will be charged through resistance 52 whenever the key 22 is depressed. The direct grid potential of tube l3, therefore, then comprises the bias potential supplied by battery 54 plus the charging potential of condenser 56. The frequency of the oscillator 3 consequently varies so long as the key is depressed or until the condenser 56 is fully charged.

It will be observed that when the key is depressed, not only is the condenser-charging circuit closed, but also the reactor tube and oscillator tube circuits are completed through the ground connection. If desired, suitable relays may be included in the keying circuit as, for example, in the manner shown in my copending application Serial No. 231,390, filed September 23, 1938, to insure a continuous change in frequency during the time of transmission of the signal.

It will be evident that with this arrangement the number of cycles of frequency change per unit time is determined by the capacity of the condenser 56 and the magnitude of the series resistance 62, that is by the time constant of the condenser charging circuit. Consequently by varying the magnitude of resistance 62, the time constant of the circuit and therefore the rate of frequency change can be varied. Further, by varying the impressed potential as by adjustment of the movable contact of potentiometer 63 the maximum magnitude of the charge on condenser 56 can be controlled, thereby controlling the range of frequency variation of the oscillator which can be obtained. Now, since the condenser potential is superimposed upon the bias provided by battery 54 it will be evident that the polarity of the condenser potential will determine whether the anode current of tube l3 shall increase or decrease, thereby determining whether the frequency of oscillator 3 shall increase or decrease. The reversing switch 64 makes it possible to obtain either an increase or decrease of frequency as may be desired.

The above frequency sweep circuit has a number of advantages over circuits for the same purpose previously proposed. The circuit permits very flexible control not only of the direction of frequency sweep, but also of the amount of frequency sweep. It also permits the obtaining of the necessary degree of frequency sweep without the use of high voltages, a voltage swing at the grid of tube 13 of about 5 volts being'adequate in most cases.

While the frequency sweep circuit just described has been shown for only one station, it will be evident that two or more frequency sweep control stations can readily be provided in the manner previously described with reference to the single frequency control arrangement. For most echo ranging purposes, however, it will usually be unnecessary to provide for the control of the length and rate of frequency sweep at more than one station. It may, however, be desirable to be able at each control station to shift from automatic frequency sweep to simple single frequency transmission. This is accomplished by means of the relay 25 previously referred to. The operating coil of this relay has one terminal connected to a source of direct current, the other terminal of the source being connected to the movable contact of a three-way switch 8| at station 30. A similar three-way switch 82 is provided at station 29. The movable member of the switch 82 is connected to the second terminal of the relay coil 80. The two stationary contacts of the two switches 8| and 82 are connected together. By this means the operator at either station 29 or station 30 by actuating the respective switches 82 and 8! can energize or deenergize the relay 25 to select either sweep frequency or single frequency control.

A modification of the reactor tube oscillator circuit shown in Fig. 2 may be employed where a very large range of frequency variation is required. In this modification the reactor tube and oscillator circuits are substantially the same as in Fig. 1. The adjustable direct potential for the grid circuit of the reactor tube I3 is, however, preferably provided by a rotary potentiometer l3 and the tuning condenser 9a in the oscillator tank circuit is made variable. The shaft of the potentiometer and the shaft of the tuning condenser are mechanically coupled together in such a manner that as the grid voltage supplied by the potentiometer is increased in a positive direction, thereby tending to increase the frequency of the oscillator 3, the capacity of the condenser So will simultaneously be decreased,

' tending further to increase the frequency of the oscillator 3, and vice versa. A very large range of frequency variation, for example, 5 to 1, can readily be obtained in this manner.

Having now described my invention, I claim:

1. In a submarine signaling system having a submarine projector and an oscillatory circuit for operating the same, remote control means for operating said system from more than one station including electrical means located and 0perated at each station for varying the oscillator frequency at will, switching means located at each station. for disconnecting the electrical means located at any other station that happens to be operating for varying the oscillator frequency and connecting the means located at vthe desired station for varying the oscillator frequency, said switching means including at each station a double pole-pole two-position switch with the contacts correspondingly interconnected and the double poles of one switch electrically connected together and to the oscillatory circuit and the double poles of the other switch individually connected respectively to the electrical means located and operated at each respective station.

2. In asubmarine signaling system having a submarine projector and an oscillatory circuit for operating the same, remote control means for 8 operating said system from more than one station including electrical potentiometer control means located and operated at each station for varying the oscillator frequency at will, said potentiometer control means being connected in common on one side to a point in said oscillatory circuit, a double-pole, two-position switch at each station with the contacts correspondingly interconnected, the double poles of one switch being connected together and to a point in the oscillatory circuit and the double poles of the other switch connected one to each of the variable taps on the potentiometer control means, whereby at will each station may take control for varying the oscillator frequency at will.

BERTRAM M. HARRISON. 

